The parent invention of this current invention discloses a volumetric 3D display system that creates volumetric 3D images by projecting whole frames of 2D images created on a stationary projection device, through an optical-mechanical image delivery system, onto a moving screen (rotating or reciprocating). The system allows creation of volumetric 3D images using conventional 2D projection optics, without the need of collimated image beams. This current invention provides new mechanisms with improved motion smoothness and simplified structure.
In the prior arts, De Montebello disclosed a system using a rotating spiral screen to create a display space and a film projector to project 2D image frames onto the spiral screen [De Montebello 1969]. The depth of its display space is limited by the depth of focus of the projector and therefore is small. Morton described another system using a rotating helical screen to form a display space and using an anamorphic lens to accommodate the variation of focal distance from an image source to the surface of the helical screen [Morton 1990]. The anamorphic lens is difficult to make and complex to assemble. Its discrete nature can also compromise image quality. Another approach projects images composed of collimated light beams directly to a moving screen [Thompson 1996]. This usually requires a laser as the light source and hence can cost more than a projector-based system. Still another approach uses a stack of electrically switchable liquid crystal display layers [Hattori 1992, Sadovinik 1998]. Another approach uses a piezoelectric-based fast focusing lens to project image frames to a stack of switchable PDLC screens [Paek 1996]. Both approaches have limited resolution because the number of LCD panels or screens in the stack is physically limited.